This invention relates to improvements in devices for rapid stepwise transport of photographic film strips and photographic print strips and the like, such as in a commercial processing laboratory wherein the strips are fed to a strip cutter or other operating device cyclically actuated in timed relation to the pauses between progressive feed increments. A broad object hereof is to provide digital precision means under direct operator control to establish and, as necessary, correct the successive transport step distances or intervals by which the drive mechanism advances the strip to the cutter or other operating device so as to present precisely the correct operating point on the strip each time to the operating device. A related object is to make such corrections with little if any interruption of the strip transport operation. The invention is herein illustratively described by reference to the presently preferred embodiment thereof; however, it will be recognized that certain modifications and changes with respect to details may be made and that certain other applications of the invention are contemplated without departing from the essential features involved.
It was known in the art heretofore to utilize rapid-acting strip feed or transport devices responsive to a digital command number to establish the desired incremental feed distance. Such feed mechanisms employed precision increment stepping motors and step counters that stopped the motor when the count reached the command value. Detection of a notch (or other mark) in the advancing strip at a detection point ahead of the operating device provided a basis to compute feed distance to the latter and thus provided the required digital command. However, for those occasions in which filmstrip or photographic print strip is not notched or otherwise marked, other means are necessary to command the drive mechanism if the important advantages of that type of rapid transport system are to be retained.
A further object hereof is to provide a simple and reliable means allowing precision corrections to be made at will in the step feed distance of the feed means through visual observation and control of a single manually adjustable indicator element. A related object is to permit making such corrective adjustments very quickly either with the strip at rest or "on the fly," that is, while under stepwise advancement by the feed mechanism. In either event adjustments are made without materially delaying or retarding system operation.
Still other objects include devising a relatively lowcost and reliable apparatus readily adaptable to existing equipment, devoid of mechanical parts subject to wear and consequent maintenance requirements, and readily implemented using components already available or easily produced.